Effect of inbred genotype on kernel development in maize-Tripsacum hybrids

--Elena P. Erygina and A. S. Mashnenkov

It was found that inbreds differed much in frequency of seed set in maize-Tripsacum crosses (MNL 63:87, 1989). In 1989 11 maize inbreds were crossed with Tripsacum dactyloides (2n=72). Ten ears were pollinated in each inbred. Depending on rate of ovary development four types of maize-Tripsacum hybrid kernels were distinguished:

1. kernels with well-developed germs and endosperms (test weight of a kernel--m=30-80mg),

2. kernels with poorly developed endosperms (m=15-30mg),

3. kernels with well-developed pericarps and initiated germs and endosperms (m=6-15mg),

4. kernels with initiation of pericarps, germs and endosperms.

All four types of kernels were included in the index-percentage of developed ovaries (Table).
 
Maize inbreds Ovaries per ear Developed ovaries, % F1 kernels with germs and endosperm, % Coefficient of kernel development, P Coefficient of compatible F1 genomes, C1
Gk26 4020 0.72 0.00 0.000 0.000
Tm10 3030 4.90 0.00 0.000 0.000
T22 2256 9.66 0.00 0.000 0.000
Gk30 1922 29.08 18.73 0.144 2.697
W23 4200 19.50 3.55 0.092 0.327
A344 3596 48.28 28.20 0.139 3.920
PLS61 3726 48.77 39.99 0.125 4.999
Gb834 2040 18.14 14.17 0.109 1.545
Hy2 3322 17.40 7.92 0.076 0.602
F2 1876 43.07 3.62 0.065 0.235
A663 5070 20.63 12.96 0.152 1.970
Coefficient of kernel development (P) was determined as a quotient of division of the value of test weight of hybrid kernels with germs and endosperms into the value of inbred per se test weight. Coefficient of genome compatibility (C1) is equal to the product of F1 kernel development rate (P) by percentage of kernels with endosperms.

Three inbreds, Gk26, Mangelsdorf's Tester 10 (TM10) and T22 showed complete incompatibility with Tripsacumdactyloides genomes. According to rate of kernel development other inbreds may relatively be divided into three groups: P = 0.65-0.92; P = 0.109-0.139; P = 0.144-0.152.

In the case of T. dactyloides ample pollen on cut maize silks, all egg cells are probably fertilized but kernel development stops at different stages of organogenesis.

In this case the value P mainly expresses rate of accumulation of stored substances in kernels. Coefficient C1 considers time that kernel development stops, i.e. stability of organogenesis. Evidently these traits are independently inherited. For instance, for inbreds PLS61 and A344 the most stable organogenesis is observed at moderate rates of stored substance accumulation in endosperms. Inbreds A663 and Gk30 are characterized by a contrasting combination of these traits.

To improve efficiency of hybridization the genetic factors governing maximum expression of both traits should be combined.

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors

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